To date, a method such that a groove that forms an origin is formed by scribing, and a three-point bending is carried out so that stress is applied in a direction in which the groove is to be spread, has been implemented as a method of dividing a semiconductor substrate into individual semiconductor elements. With this kind of mechanical processing method, however, there is a problem in that when a division interval is short, the stress of the three-point bending does not act effectively, and a large number of division failures occur. Because of this, there are expectations for a division method using laser irradiation as a division method to take the place of the mechanical processing method.
As an existing example of a division method using laser irradiation, a method such that a projected division line of a semiconductor substrate is irradiated with an ultra-short pulse laser light, thereby causing the material of the substrate to vaporize, is disclosed in Patent Document 1. Also, a method such that, by an interior of a semiconductor substrate being irradiated with a laser light and a focal point being moved along a projected division line of the semiconductor substrate, a crack region (or melting process region) is formed in the substrate interior, after which the substrate is divided by an external force being applied to the substrate, is disclosed in Patent Document 2.